Crenel refers to the teeth-like indentation found on the top of a castle wall, which was designed to provide protection during a siege. Some of the synonyms for crenel include battlement, embrasure, loophole, merlon, and parapet. These words are used to describe the different structures that make up the crenelated wall. A battlement refers to the entire wall structure with alternating solid and open spaces. An embrasure is a recessed opening in the wall that allows for the firing of weapons. A loophole is an opening that allows archers to fire their arrows through the wall. Merlons are the solid portions of the battlements, while the parapet is the topmost portion of the wall.